|Daniels, K - VPI&SI|
|Mcgilliard, M - VPI&SU|
|Meyer, M - CORNELL UNIVERSITY|
|Van Amburgh, M - CORNELL UNIVERSITY|
|Akers, R - VPI&SU|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2008
Publication Date: February 1, 2009
Repository URL: http://hdl.handle.net/10113/37589
Citation: Daniels, K.M., Mcgilliard, M.L., Meyer, M.J., Van Amburgh, M.E., Capuco, A.V., Akers, R.M. 2009. Effects of Body Weight and Nutrition on Histological Mammary Development in Holstein Heifers. Journal of Dairy Science. 92:499-505. Interpretive Summary: Tissue sections were prepared from mammary tissue samples from heifers reared on either a moderate or high dietary treatment, and sacrificed at one of five body weights to determine effects of rate of gain and body weight on parenchymal tissue development. Percentages of mammary structural components of interest did not differ by BW or treatment, nor was there an interaction between treatment and BW. Our findings support the hypothesis that the length of time between birth and slaughter plays a predominant role in determining developmental characteristics of heifer mammary parenchyma irrespective of rate of gain.
Technical Abstract: Our objective was to determine effects of rate of gain and body weight (BW) on mammary parenchymal tissue development. Mammary tissue samples were available from heifers (n = 54) reared on one of two dietary treatments, restricted (R) 650 g/d or elevated (E) 950 g/d of daily gain), and slaughtered at 150, 200, 250, 300, or 350 kg BW. At slaughter, mammary parenchymal samples were excised, preserved, prepared for histology, and stained with hematoxylin and eosin. Representative digital images of tissue sections were captured for analysis. Tissue areas occupied by interlobular stroma, epithelium, lumen, and intralobular stroma were measured (mm2) and the numbers of epithelial and luminal structures per image were tabulated. Mean percentages of mammary parenchyma occupied by interlobular stroma, epithelium, lumen, and intralobular stroma were 28, 20, 7, and 45%, respectively; percentages did not differ by BW or treatment, nor was there an interaction between treatment and BW. Number of epithelial (31 ± 6 vs. 47 ± 5) and luminal (24 ± 5 vs. 38 ± 4) structures per image increased between 150 and 350 kg BW. For heifers slaughtered between 150 and 350 kg of BW, alterations in the rate of gain between 650 and 950 g/d, accomplished by feeding varying amounts of the same diet, had no significant effect on tissue characteristics or the pattern of mammary parenchymal development. Perhaps with other diets, changes in parenchymal tissue composition would be noted. Our findings support the hypothesis that the length of time between birth and slaughter plays a predominant role in determining the tissue characteristics of heifer mammary parenchyma, irrespective of rate of gain.